Folded, laminated electrical cable sheath having abutting edges of one lamination unwelded



Oct. 8, 1968 F. F. POLIzzANO 3,405,228

FOLDED, LAMINATED ELECTRICAL CABLE SHEATH HAVING ABUTTING EDGES OF ONELAMINATION UNWELDED Filed Nov. 29, 1967 Il CORE REEL 24/30; lsq

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ATTORNEYS.

United States Patent O "tee 3,405,228 v l FOLDED, LAMINATED ELECTRICALCABLE- SHEATH HAVING ABUTTING EDGES OF l ONE LAMINATION UNWELDED I FredF. Polizzano', Allendale, NJ., assignorto General Cable Corporation, NewYork, N.Y., a corporation of New Jersey Continuation-impart ofapplication Ser. No. 478,820,

Aug. 11, 1965. This application Nov. 29, 1967, Ser. No. 686,670

11 Claims. (Cl. 174-106) ABSTRACT OF THE DISCLOSURE This specificationdiscloses an improved construction for shielded electric cable that hasametallic sheath longitudinally wrapped around the cable with a butt seamwhich is welded. The sheath is laminated but instead of having the outerlamination Wider than any inner lamination, so that the welded seam hasno shielding under it, this invention has the outer welded lamination ofhigher electric conductivity and lower melting point than the underlyinglamination, and has the underlying lamination extending under the entirearea of the butt welded edge portions of the outer laminations.The'preferred construction has copper as the outerv lamination. and .a`stainless steel as the inner lamination with only the copper welded.

. Related patents or applications.

This application is a continuation-in-part of Ser. No. 478,820, led Aug.11, 1965, now abandoned.

This invention'is an improvement on the method and product `disclosed inlachimowicz No. 3,183,300. In that patent, a core of insulated cable issurrounded by a laminated metallic sheath having an outer lamination ofsteel and an inner lamination which is preferably aluminum.

The sheath has a butt weld of the outer lamination, but" Briefdescription of the invention This invention is an electric cable with-an improved welded sheath that combines in one sheath the properties of(l) being gashtight; (2) having high electrical conductivity along itssurface; (3) providing a ferro-magnetic shield; and (4) having highmechanical strength. TheV sheath can be made with either a cylindricalor with a generally circumferentially corrugated wall, depending uponthe degree of flexibility necessary.

This invention uses a laminate for the sheath which was formerly used oncables of the type Where the sheath has a lap seam which is unwelded andwhich is held closed and protected from moisture by an outer plasticjacket. With this invention, such a laminate is welded and its use in awelded sheath obtains new and unexpected advantages.

One of these advantages is that the outer laminate can be welded withoutwelding the inner laminate, and since the outer laminate has a lowermelting point than the inner laminate, the Weld can be made at atemperature that does not heat the inner laminate to a degree which willmake it contaminate the weld and the edge portions of the inner laminatecan, therefore, extend under the entire area of the edge portions of thewelded seam. It is not necessary to cut back the inner laminate as inthe 3,405,228 Patented Oct. 8, 1968 Jachimowicz patent (supra) and thusthe welded seam is much stronger because the welded edges are reinforcedby the adjacent inner lamination.

The preferred construction of the invention has an inner laminate ormild steel, stainless steel (magnetic type) or other ferro-magneticmetal and an outer laminate of copper or some other metal which is abetter conductor of electricity than the ferro-magnetic material andwhich is highly resistant to `destructive corrosion. The sheath can bemade with three laminates, the outer and inner ones being copper and themiddle laminate being ferromagnetic metal sandwiched between the copperlaminates.

The invention also provides an improved method of making an electriccable of the character indicated.

Other objects, features and advantages of the invention will appear orbe pointed out as the description proceeds.

Brief description ofthe drawing In the drawing, forming a part hereof,in which like reference characters indicate corresponding parts in allthe views:

FIGURES 1a and 1b are diagrammatic showings of apparatus for makingelectric cable with a composite sheath in accordance with thisinvention;

FIGURE 2 is a greatly enlarged top plan view of the forming and weldingapparatus shown in FIGURE la;

FIGURES 3-5 are greatly enlarged, fragmentary sctional views throughdifferent kinds of composite -metal strip from which the sheath can bemade;

FIGURE 6 isa greatly enlarged sectional View through the cable with themetallic sheath applied and welded, the section being taken along thesection line y6 6 of FIG- URE la; and

FIGURE 7 is a flow diagram.

Description of the preferred embodiments FIGURES la and 1b showapparatus for making an electric cable with a composite metal sheath. Apreformed core 10 of assembled electrical conductors is unwound from acore supply reel 1-1 and is advanced across a supporting tray 12 toforming and welding apparatus. A composite metal strip 16 is unwoundfrom a strip supply coil 18 and with the composite metal strippreferably in a transversely flat condition as it is passed through adegreasing tank 20.

Beyond the tank 20, the composite metal strip 16 passes throughsuccessive roll stands of forming apparatus 22; and the core 10 is fedinto the forming tube as the core 10 and forming strip 16 advance inunison through the forming and welding apparatus.

In the forming apparatus, the longitudinal edges of the strip 16 arebrought together to make a longitudinal butt seam, and this seamadvances through a welding station 30. A roll pass 26, formed by tworolls 32 on opposite sides of the formed tube holds the tube or sheathwith the seam edges together and the formed sheath is indicated by thereference character 16.

At the wel-ding station 30 there is an electrode 36 held in a support38. This electrode has its lower end positioned over the seam of thesheath -16 and shielding gas is flowed over the region of the weld froma nozzle 40.

At least the outer lamination of composite metal of the sheath 16 iswelded along the longitudinal seam and this welding will be explainedmore fully in connection with FIGURE 6. It is an advantage of theinvention that it can be carried out so as to close the seam of thesheath by welding the metal having the lower melting point and thesheath is preferably formed by bending the strip transversely in adirection which locates the lower-meltingpoint metal on the outside ofthe sheath. Where the composite metal has three laminations, the innerlamination may also be a .low-melting-point metal and the manner inlwhich this is welded will be explained in connection with FIGURE 6.

After the sheath 16 has been welded by the electrode 36, the sheath,with the core located within it, is advanced by an endless belt feeder42 (FIGURE 1b), having clamp-type grippers 44 connected at spacedlocations around an endless belt 46. The feeder 42 advances the sheath16 to a corrugator 48. If a ilexible sheath is required, the corrugator48 is equipped to form generally circumferentially extendingcorrugations 50; and the cable with this exible sheath is wrapped on atake-up reel 52.

If substantial flexibility is not required, then the corrugator is notused and the tube is sized through a die and the sized sheath is coiledfor shipment in the same manner as conventional, uncorrugated tubing.

Since the corrugating of the sheath 16' reduces its axial length, therate of feed of the core 10 is substantially slower than the `rate offeed of the strip 16 when the forming and welding apparatus is used withcorrugating rolls beyond the welding station. When the sheath is sizedafter welding, the diameter is ordinarily reduced to some extent andthis elongates the sheath and makes it necessary to feed the core 10tothe forming and welding apparatus at a higher speed than the strip 16is fed.

When the sheath is to be corrugated, the forming apparatus is used withthe forming roll passes adjusted to produce a tube diameter in which thecore tits somewhat loosely. When there is to be no corrugating ofthesheath, the tube can be formed snugly around the core 10 but the heatapplied in welding must be kept to a degree low enough to avoid damageto the insulation which is adjacent to the seam. This invention makes itpossible to weld the sheath closed with substantially less heat than isrequired where steel edges are welded. The copper edges Iweld at lowertemperature than steel and the underlying steel laminate serves as aheat sink for carrying away heat to protect the insulation fromoverheating when the sheath is formed snugly around the core beforewelding.

The composite metal strip 16 is passed through the degreasing tank 20prior to forming and welding, this tank and its operation being similarto that described in my co-pending application Ser. No. 428,757, ledJan. 28, 1965 for Electric Arc Welding of Aluminum. The tank isstructurally similar to commercially available vapor degreasers and nofurther description of it is necessary for a complete understanding ofthis invention.

The roll stands of the forming apparatus are supported from `a base 76which supports a frame 78 connected to the base 76 by brackets 80. Thereare three roll stands r 81, 82 and 83 with upper and lower rollsindicated by the same reference characters as the roll stands but with aprime appended. The rolls in these first three stands 81-83 are mountedfor rotation about horizontal axes.

A fourth roll stand 84 has rolls 84 located on opposite sides of theforming strip 16 and these rolls 84 are supported on vertical axes andpreferably with adjustment toward and from one another in accordancewith conventional practice for tube-forming mills.

A last roll stands 24 of the forming apparatus has rolls 24 which bringthe edges of the strip 16 closer together while the core 10 is fed intothe forming tube or sheath at a location where the seam is still openwide enough to receive the core, as shown in FIGURE 2.

At the welding station 30, the strip 16 is fully formed by the time itpasses through the roll pass 26; and at a location adjacent to this rollpass 26, the seam of the formed tube or sheath is welded, as previouslyexplained.

FIGURE 3 shows the metal strip 16 in section. This strip includes anouter lamination 91, a middle lamination 92 and an inner lamination 93.These laminations are preferably bonded together over the areas of theirconfronting faces, as indicated by the heavy lines 95. The manufactureof such composite metal strip is well known and no description of it isnecessary for a complete' understandingof this invention. j

The lamination 91 is preferably made of copper and the lamination 92 ismade of stainless steel (magnetic type). The lamination 93 is also madeof copper. 4In the construction shown in FIGURE 3, all of thelaminations 91, 92 and 93 are of the same thickness.

FIGURE 4 shows a modified construction for the composite metal strip,indicated by the reference character 16a. This strip has a thin outerlamination 96, a thick middle lamination 97 and a thin innerflamination98. These laminations can be made of the same kind of metal as in FIGURE3 but the cost of the material can be substantially reduced by havingthe middle lamination 97 made of mild steel. The use of thin copperlaminations 96 and 98 still further reduces the cost of the strip 16aand the mild steel of the middle lamination 97 is protected againstcorrosion by the copper laminations 96 and 98 on both sides of the mildsteel lamination 17.

FIGURE 5 shows still another modication for the composite metal strip;the strip of FIGURE 5 being designated by the reference character 16b.In this construction there is an outer lamination 101 of copper and aninner lamination 102 of mild steel or other ferromagnetic material. Inthis construction, the copper lamination 101 comprises 25% of thethickness of the strip 16b; and the ferro-magnetic lamination 102comprises of the thickness of the strip.

It will be understood that the choice of laminations depends upon theservice to which the cable will be put. If conditions require that thesheath have high electrical conductivity for substantial current, thenit is necessary to have the copper, or other good electrical conductor,in a lamination of substantial thickness. If service conditions do notrequire a substantial cross section of copper, or if conditions are nothighly corrosive, then the cost of sheathed cable can be reduced bymaking the copper or other highly conductive and corrosive-resistantlamination thin, as compared with the lamination which is made offerrous metal.

FIGURE 6 shows the core 10 with a plurality of individually insulatedmetal conductors located in an insulating jacket 112. Space between theinsulated conductors 110 and between the outer ones of these conductorsIand the jacket 112, contains filler material 114, in accordance withconventional cable construction practice.

The sheath 16 has the outer lamination 91 welded at but the seam betweenthe edges of the middle lamination 92 are not welded and this unweldedseam is indicated by the reference character 118, in FIGURE 6. The innerlamination 93 is welded as indicated by the continuous section 119underthe seam 118. This condition arises from the fact that the copperof the laminations 91 and 93 has a much lower melting point '(1860" F.)than the melting point of the steel lamination 92 (2600#- 2750" F.).

When welding heat is applied to weld the seam along the edges of theouter lamination 91, heat flows inward by conduction through the middlelamination 92 and into the inner lamination 93. This heating byconduction is suicient to melt and weld the inner lamination 93 beforethe seam 118 in the middle laminate 92 becomes hot enough for welding.Since the welding of the laminations 91 and 93 completely encloses themiddle lamination 92, it is not necessary that the seam 118 be weldedunless the sheath is to be subject to service where mechanical strengthwould make it necessary to weld the seam 118. Where such is the case,the sheath can be made larger than the outside of the jacket 112 so thatthere is a clearance between the core 10 and the longitudinal seams ofthe sheath at the time of welding; and the sheath can be sized to bringit down snugly on the core 'after the weld is completed. For mostpurposes, such mechanical strength is not necessary.

When the core 10 is surrounded by a sheath having only two laminations,such as the construction shown in FIGURE 5, the welding of the edges ofthe copper lamination 102 is sucient to make the sheath gas-tight andexcept for special services, the welding of the edges of theferro-magnetic lamination 102 is not necessary. Dissipation of heatthrough the mass of the lamination 102 protects the jacket of the corefrom excessive heating during welding of the seam edges of the outerlamination 101.

FIGURE 7 is a llow diagram showing the successive steps of forming andwelding the composite metal strip to form the sheath, and showing thethird step of eithercorrugating or sizing the tube.

The preferred embodiment of the invention has been illustrated anddescribed, but changes and modications can be made and some features canbe used in diterent combinations without departing from the invention asdefined in the claims.

What is claimed is:

1. In 'an electrical cable of the class having a core which includes aconductor and electrical insulation surrounding the conductor, andhaving a composite metallic sheath folded longitudinally around the corewith the edges of the sheath in abutting relation with one another alonga longitudinal seam, the improvement which comprises (a) the sheathincluding metal laminations metallurgically bonded to one another,

(b) said laminations being of substantially equal width Iand the edgesof each lamination abutting one another along said seam,

(c) the outer lamination having a higher electrical conductivity andlower melting point than the underly ing metal lamination, and being ofcorrosion-resistant metal,

(d) the abutting edges of the outer lamination being welded together tomake the sheath waterproof, and

(e) the abutting edges of the underlying lamination being immediatelybelow the edges of the outer lamination and being unwelded to oneanother but being held together by the metallurgical bonding tothe edgeportions of the outer lamination, which edge portions are welded to oneanother.

2. The electric cable described in claim 1 characterized by the outerlayer of metal being copper with its edges welded together along thebutt seam and the layer of metal that is bonded to the copper being aferro-,magnetic metal.

3. The electric cable described in claim 2 characterized by theferro-magnetic metal being a magnetic-type stainless steel.

4. The electric cable described in claim 1 characterized by the sheathbeing made of three laminations of metal including two laminations thatare bonded to opposite sides of a middle sandwiched layer over theconfronting faces of the laminations, said two laminations being moreresistant to corrosion than is the sandwiched layer.

5. The electric cable described in claim 4 characterized by the sheathbeing a tube and the outer and innermost laminations having lowermelting points than the sandwiched layer and each having its seam edgeswelded together along the butt seam of the tube to form continuoussurfaces over the middle sandwiched layer.

6. The electric cable described in claim 1 characterized by an assemblyincluding a plurality of insulated conductors within the sheath andhaving spaces between and around the insulated conductors filled withfiller material, anda jacket of electrical insulation applied snuglyaround the insulated conductors and filler material and completelylilling the space between said assembly and the inside 6 surface of theinner lamination of the composite metal sheath.

7. The electric cable described in claim 1 characterized by the outerlamination being copper and the inner lamination being a ferromagneticmetal and being substantially thinner than the copper lamination.

8. The electric cable described in claim 1 characterized by the outerlamination being copper and the inner lamination being a ferro-magneticmaterial and being substantially thicker than the copper lamination.

9. The method of making an electric cable with a protecting sheath thatincludes a composite strip having substantially co-ex'ensive laminationssurface metallurgically bonded to one another over their confrontingsurfaces, the strip having a layer of ferro-magnetic ,material and alayer of other metal that is a better conductor of electricity than isthe ferro-magetic material and that has a lower melting point, whichmethod comprises advancing a continuous insulated conductor through aforming and welding station, feeding the composite strip to the formingand welding station in unison with the insulated conductor, forming thecomposite strip around the insulated conductor as a tube with alongitudinally extending seam having the seam edges of both layers inabutting relation with one another, applying heat to the seam insufficient intensity to weld together the abutting edges of the outermetal strip which has the lower melting point, and limiting thetemperature of welding by heating the metal to a temperature greaterthan the melting point of the outer strip and less than the ,meltingpoint of the ferro-magnetic material.

10. The method describe-d in claim 9 characterized by forming thecomposite strip with a diameter substantially equal to the outsidediameter of the insulation within the sheath whereby the sheath, as itis formed, substantially touches the insulation around the entirecircumference of the sheath including the abutting seam edges, formingthe strip in a direction which locates on the outside of the tube ametal of the strip which has a lower melting point than the other, andwelding the outer lowermelting-point metal to close the seam whilelimiting the heat to a degree which avoids welding of the edges of theinner lamination and damage to the insulation on the conductor withinthe sheath.

11. The method described in claim 9 characterized by feeding to theforming and welding station a composite metal strip which has threelaminations, the inner and outer laminations being made of metal oflower melting point than the middle lamination, and welding the seamedges of the outer lamination by direct application of heat from outsidethe tube, and welding the seam edges of the inner lamination byconduction of heat through the middle lamination, the heat being limitedto a temperature less than the melting point of the lmiddle lamination.

References Cited UNITED STATES PATENTS 2,576,163 11/1951 Weston et al.174-36 X 2,589,700 3/1952 Johnstone 174-106 3,050,834 8/1962 Ulam29-196.3 3,165,828 1/1965 Kennedy 29-196.3 3,183,300 5/1965 Jachimowiczet al. 174-106 3,272,911 9/1966 Rollins et al 174-106 FOREIGN PATENTS1,337,816 8/1963 France.

LEWIS H. MYERS, Primary Examiner. A. T. GRIMLEY, Assistant Examiner.

